i toentny Patterns or relationship Concepts Calorimetry, heats of reaction, stoi

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i toentny Patterns or relationship Concepts Calorimetry, heats of reaction, stoichiometry Introduction In this experiment, you will explore the way in which the enthalpy change for a reaction can be used to uce the products of a reaction system, then you will apply what you learn to determine the stoichiometry of a different, but related reaction system. Under investigation in the Skills portion of this experiment is the reaction between sodium sulfite and dilute household bleach, an aqueous solution of sodium hypochlorite. The hypochlorite ion, OCI(a) is an oxidizing agent, that is, it takes away the electrons lost by the sulfur atom in SO3 The sulfur atoms in sulfite, SO,", have an oxidation state of +4. Since +6 is the only higher oxidation state for sulfur, it to assume that sulfite will be oxidized to sulfate, SO. Your objective is to determine whether the chlorine atom in OCI is converted to chloride ion, CI, or to molecular chlorine, Cl2 first step in your analysis will be to determine the enthalpy changes that result when the reactant olutions are mixed in varying proportions. From the value of q for each combination, and from knowledge of the number of moles of each reactant present, you will be able to calculate an observed alue of AH, in kJ mol, for each trial. The combination that gives the greatest value of AH will be the one that has the correct reaction stoichiometry. Because the stoichiometry depends on the oxidation stat of sulfur in the products, you can use this stoichiometric ratio to determine whether chlorine or chloride results from the oxidation of sulfite. u will mix the reactants in a series of volume ratios and measure the temperature change in each case For each 0.50 M, th in which 10.0 mL of sodium sulfite is added to 20.0 mL of diluted bleach would have a 1:2 mole ratio of sulfite ion to hypochlorite ion The Procedure assumes that you will use an interfaced thermistor probe. If instead you u analog) thermometer, you will and the maximum temperature reached by each solution combination trial you will use a total of 30.0 mL of the combined solutions. Since both reactant solutions are e volume ratio will be the same as the mole ratio for that combination of reactants. Thus, a trial se a digital (or need to manually record the initial temperature of the first reactant solution

Explanation / Answer

Hypochlorite is an oxidizing reagent and in reaction with the sulfite , sulfite is oxidized to sulfate and the chlorine atom in the OCl– ion may either become Cl2 or Cl-

To determine the products of the reaction write the balanced equations for the formation of each of the two possible chlorine products-

2 NaOCl (aq) + Na2SO3 (aq) + 2 H2O (l) Na2SO4 (aq) + Cl2 (g) + 2 NaOH (aq)

NaOCl (aq) + Na2SO3 (aq)     NaCl (aq) + Na2SO4 (aq)

You can clearly see the mole ratio of ocl:SO3=1:1 for the reaction with Cl- as product ,while for the other it is 2:1.

The mole ratio that produces the maximum heat of the reaction is considered to be the actual mole ratio of the reactants.So you need to calculate the mole ratio of ocl:SO3 for each trial and also calculate the Q (reaction)=-Cp*T per mole hypochlorite used up.The mole ratio is then determined basis the highest heat of reaction.

B) The trial with mole ratio 1:1 giving highest heat of the reaction has Cl- as the product.And the one with mole ratio 2:1 having highest heat is for Cl2 as the product.

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